The present invention relates to a decorative sheet having a metalescent appearance and a metal layer which is included inside the sheet and observed through a light-transmitting covering film.
Decorative sheets are known, which comprise a covering film layer containing a flexible resin and a metal layer provided on the back of the covering film layer and has a metalescent appearance, and in which the metal layer can be observed through the covering film.
One of the characteristics of such decorative sheets is that a resin layer in direct contact with the metal layer comprises a resin having relatively high heat resistance and good adhesion to the metal layer to prevent clouding (whitening) of the metal layer under high temperature conditions.
For example, Japanese Patent Publication JP-A-1-174584 discloses a decorative sheet comprising a laminate film including a vinyl fluoride resin and a covering layer which has good printing properties, and a metal deposition layer adhered to the vinyl fluoride resin side. This decorative sheet uses the vinyl fluoride resin having high heat resistance and good adhesion to the metal layer as a bonding layer between the covering layer and metal layer to adhere these layers. Thus, the clouding of the metal layer is prevented. However, the kinds of the resins for the covering layer is limited, since those having good adhesion to the vinyl fluoride resin should be used. A vinyl chloride resin is exemplified as a resin for the covering layer, but the above patent application does not disclose how to adhere the vinyl chloride resin and vinyl fluoride resin.
U.S. Pat. No. 5,164,245 (Suzuki) discloses a decorative sheet which uses, as a covering film, a laminated film comprising a polymer alloy layer of polyvinylidene fluoride (PVDF) and polymethyl methacrylate (PMMA). That is, the decorative sheet disclosed uses a film comprising a PMMA-rich first alloy layer as the outermost layer, and a PVDF-rich second alloy layer which is adhered to the metal layer. It may be possible to use the above covering film as a bonding layer, and a vinyl chloride film as the outermost covering film, since the first alloy layer has relatively good adhesion to flexible resins such as the vinyl chloride resin.
However, extruded films or co-extruded films are usually used, since the above fluororesins are dissolved into solvents with difficulty. In such a case, the films have low smoothness. Thus, embossing or other heat treatment is necessary to achieve the high mirror smoothness, but such treatment may flaw the surface of the film. Furthermore, the fluororesins are expensive. Flaws on the bonding layer deteriorate the appearance, since the metal layer is observed through both the covering film and bonding layer.
Japanese Patent Publication JP-A-7-112521 discloses a decorative sheet comprising a bonding layer made of an urethane resin having a siloxane bond in the molecule. The urethane resin has very good effects on the prevention of the above clouding of the metal layer, and can be filmed by coating. Thus, the urethane resin layer is less flawed during the production process than the fluororesins. In addition, the urethane resin is less expansive than the fluororesins. However, this publication does not concretely describe how to adhere the bonding layer and covering film, when the vinyl chloride resin film is used as the covering film.
It has been found that the adhesion between the vinyl chloride resin and the above urethane resin as disclosed in Japanese Patent Publication JP-A-7-112521 is low. Thus, a need exists in the art to find a decorative film that is flexible and can have a patterned metallic layer.
Vinyl chloride resin film is very useful as the covering film of the decorative sheet, since (1) it satisfies the required properties for the decorative sheet, such as weather resistance, (2) a variety of satisfactorily used pigments can be used for coloring the film, and (3) the price of the decorative sheet can be reduced.
Thus, one aspect of the present invention is a decorative sheet which comprises a vinyl chloride resin film as a covering film, and prevents clouding (whitening) of a metal layer under high temperature conditions.
The present invention provides a decorative sheet comprising:
(a) a light-transmitting covering film which comprises a vinyl chloride resin,
(b) a light-transmitting bonding composite layer which is adhered to the back of said covering film, and
(c) a metal layer which is adhered to the back of said bonding composite layer, wherein
said bonding composite layer comprises the first resin layer adhered to said covering film, and the second resin layer adhered to said metal layer, said first resin layer comprises a saturated polyester or an aminoethylated resin, and
said second resin layer comprises (i) a polyester having a siloxane bond in a molecule or (ii) a polyurethane resin having a siloxane bond in a molecule and a polyester unit.
The present invention can effectively improve the clouding of the metal layer and the adhesion of the metal layer to the covering layer, since the bonding composite layer, which adheres the metal layer and covering film comprising the vinyl chloride resin, has the above structure.
Herein, the xe2x80x9cvinyl chloride resinxe2x80x9d includes a homopolymer of vinyl chloride, and copolymers comprising vinyl chloride units.
The first resin layer of the bonding composite layer comprises a saturated polyester or an aminoethylated resin, and thus has good adhesion to the covering film comprising the vinyl chloride resin.
The second resin layer of the bonding composite layer comprises (i) a polyester having a slioxane bond in a molecule or (ii) a polyurethane resin having a siloxane bond in a molecule and a polyester unit, and thus prevents the clouding (whitening) of the metal layer under the high temperature conditions. Furthermore, the adhesion of the second resin layer to the first resin layer increases.
According to the present invention, a film comprising a vinyl chloride resin can be used as a covering film, and a decorative sheet is provided, which does not suffer from peeling off at any interface of the covering film, bonding composite layer and metal layer, and prevents the clouding of the metal layer during the use (even under the high temperature conditions). The first and second resin layers of the bonding composite layer are preferably formed by a coating method to effectively increase the adhesion between these resin layers.
Further features and advantages of the invention will be described in respect of embodiments described with reference to the following drawing.